Waring added, “Theorems of this kind will be very hard to prove, because of the absence of a notation to express prime numbers.” (Reading the passage, Gauss uttered his telling comment on “notations versus notions.” Implying that in questions of this nature it was the notion that really mattered, not the notatione.) Despite Waring’s pessimistic forecast, soon afterward Lagrange (1771) gave a proof of what in literature is called “Wilson’s theorem” and observed that the converse also holds. Perhaps it would be more just to name the theorem after Leibniz, for there is evidence that he was aware of the result almost a century earlier, but published nothing on the subject.